In manufacture of an SOI wafer by using an ion implantation delamination method, an SOI wafer having an SOI layer with high thickness uniformity can be manufactured by bonding, through an oxide film, a wafer (a base wafer) to another wafer (a bond wafer) into which a hydrogen ion, a rare gas ion, or the like is implanted, and then delaminating the ion-implanted wafer at the ion-implanted layer.
In the manufacture, when there is an extraneous substance, an organic substance, a scratch, or a fine crystal defect caused by the wafer at a bonding interface, fine cavities are formed at the bonding interface, and defects called voids or blisters are formed on the surface of the SOI layer when the wafer is delaminated.
The void is a concave defect where a cavity penetrates from the SOI layer surface to the base wafer through a BOX layer (a buried oxide film layer). The blister is a swelled part of the SOI layer due to the fine cavity formed at the bonding interface. In case of the blister, the cavity is not formed in the SOI layer.
The surface of the SOI wafer is rough just after the delamination, and a device circuit cannot be formed on the SOI wafer surface without treatment. As a method for improving the surface roughness of the SOI layer surface, there is an annealing method in which a high temperature heat treatment is performed under an atmosphere containing an argon gas. By the annealing method, the SOI layer surface can be flattened and the thickness uniformity of the SOI layer obtained by the ion implantation delamination method can be kept high (See Patent Document 1).